Pollution of Water by Agriculture

• Vicki Chapman

• Vanina Guevel

• Anne Newson

• Tony

Situation• Before : organic waste as fertilizers

• environment not a priority

• Now : intensive agriculture

• improved techniques

• mineral fertilizers

• pesticides

• tests available

How serious is the problem?

What factors pollute water?

• Nutrients• Slurry• Pesticides• Chemicals• Milk effluents

• Silage effluents• Animal carcasses• Heavy metals• Erosion• Seeds

Causes of all farm pollution incidents 1987-1991

NutrientsNutrients

• Main nutrients - nitrogen, phosphorus, potassium

• Source - fertiliser, manure, rainfall, sewage, silage, etc.

• EC Limit - rivers must not exceed the 50 mg N /litre of water

• Stimulate crop growth. A limit of 250 kg total N/year/ha is recommended from livestock manures

•  The loss of the nutrients through soil percolation and land runoff, into the waterways causes disruption to the balance of the aquatic habitat.

Slurry• Source – a mixture of

animal dung and urine, Est. 200 million tonnes undiluted excreta produced annually in UK, 50% slurries.

• Most slurry stored in earth bank lagoons estimated total volume is 15.5 million m3

• Virtually all livestock waste is recycled to the land causing 17% of water pollution from agriculture to come from slurry.

• There is a restriction of 10m 'no spreading' zone adjacent to all water courses, direct spillage is highly prosecuted.

• Improvements in available grants have improved slurry stores, decreasing incidence from 99 incidents in 1991 to 28 in 1996.

PesticidesPesticides

• Herbicides

• Fungicides

• Insecticides

• Molluscicides

• Rodenticides

• Growth regulators

• Sheep dips

• … about 450 different products

• Get into river by run-off into drains, leaching from soil, spray drift into watercourse, washings

• High persistence and toxicity• Kill fish, amphibians, invertebrates and plants• Accumulation in lipids

and sediments

• Trace concentrations hard to measure• Long-term effects often unknown

Milk and chemicalsMilk and chemicals

• Milking parlour washing effluents

• Waste milk spread on the fields

• Udder wash• 400x more polluting

than untreated domestic sewage

Silage effluent

• Very harmful and concentrated pollutant

• BOD level = 30,000 – 80,000mg/l. Compare to 20-60mg/l for treated sewage.

• Very corrosive. Hard to break down. Kills fish.

Erosion

• = the wearing away of the soil by wind/water

• Soil clogs waterways• Excludes light from

water• Aquatic plants die• No oxygen for fish

and other aquatic life

SummarySUMMARY

Conclusion:How to reduce pollution

• Agricultural animals should have no direct contact with running water courses.

• Silage and slurry containers should be 100% leak-proof.

• Organic wastes, fertilisers, etc. should not be applied closer than 10m from the river (buffer strip) or 50m from wells or bore holes.

• No intensive agriculture in “High risk areas” e.g. frozen ground, floodplain, etc.

• Better use of pesticides

• Plant new crops in stubble to reduce ploughing (see right)

Laws controlling pollution

• Water Act 1989 – Farmers can be fined up to £20,000 for causing pollution!

• Environmental Protection Act 1990 – an integrated pollution control system for safe disposal of wastes.

• Classification of pesticides – – Class I : forbidden (HCH, DDT, etc.)– Class II : to be reduced (PCSDs, etc.)

Hope for the future